1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a light emitting diode (LED) package that can be used as a backlight unit of an LCD and a lighting apparatus, a manufacturing method thereof, and an LED array module using the same.
2. Description of the Related Art
LEDs are popular in the fields of advertising and electronics due to their long lifespan and low power consumption. There have also been attempts to use LEDs in backlight units of LCDs. It is also expected that LEDs will be used in indoor or outdoor lighting apparatuses in the near future. As the application range of LEDs is expanded, there are increasing demands for LED packages which are compact and can easily dissipate heat.
LEDs used in backlight units for LCDs or in lighting apparatuses require high power consumption. However, when the temperature rises, the performance of LEDs exponentially decays. Therefore, thermal management of LED packages is important.
FIG. 1 is a schematic cross-sectional view illustrating one example of a conventional LED package. Referring to FIG. 1, the LED package includes an LED 1, a heat spreading member 2 on which the LED 1 is mounted, leads 3 and 3′, wires 4 and 4′ for electrically connecting the LED 1 to the leads 3 and 3′, and a body 5 surrounding the heat spreading member 2 and the leads 3 and 3′.
The upper and lower portions of the heat spreading member 2 are exposed. An insulation layer 6 is disposed on the heat spreading member 2. The LED 1 is bonded to the center of the insulation layer 6 by an adhesive 7. First ends of the leads 3 and 3′ are disposed at both sides of the insulation layer 6. The second ends of the leads 3 and 3′ are externally protruded from both sides of the body 5. The wires 4 and 4′ are installed to connect the LED 1 to the first ends of the leads 3 and 3′. Although not illustrated, a cap for sealing up the LED 1 can be installed over the upper portion of the body 5.
The LED package is mounted on a substrate 10 and the second end of the leads 3 and 3′ are mounted on soldering pads 11 and 11′. In addition, solder 12 is disposed between the heat spreading member 2 of the LED package and the substrate 10. The heat generated in the LED 1 is dissipated to the atmosphere through the heat spreading member 2, the solder 12, and the substrate 10.
However, conventional LED packages, such as illustrated in FIG. 1, have relatively long heat transfer paths (e.g. LED-insulation layer-heat spreading member-solder-substrate). As a result, conventional LED packages exhibit low heat dissipation performance due to an increase in thermal resistance, and thus are not suitable for high power LED packages.
Thermal resistance Rth can be represented by Rth=L/(k*A). That is, when the thickness or the heat transfer path L decreases, and when the thermal conductivity k and the heat transfer area A increase, the thermal resistance Rth decreases. However, in a conventional LED package, the heat transfer path is lengthened by the thickness of the package itself and the substrate, and contact thermal resistance between different materials of LED package increases. Therefore, the overall thermal resistance of LED package increases.
When heat dissipation performance of an LED package is low, the LED lifespan is reduced, and peripheral components may deteriorate and become thermally deformed due to the high temperature, which may cause fatal damages to the system.
Additionally, conventional LED packages require many connections by wire bonding process. When an LED array module is formed by using such conventional LED packages, the number of assembly processes required, including a process for soldering the plurality of packages on the substrate, is large, and thus the production cost is high.